Inserting -(CH₂)_<i>n</i>- (<i>n</i> = 2, 3, 4) Spacers into the Reactant Mercapto-methyltetrazole Ligand for Tuning the Multinuclear Ag^I Clusters in Keggin-Based Compounds

Abstract

Four SiMo₁₂O₄₀^4– (SiMo₁₂)-based compounds, namely, [Ag₆Cl₂(mmt)₄(H₄SiMo₁₂O₄₀)­(H₂O)₂] (<b>1</b>), [Ag₄(bmte)₂(H₂O)₂(SiMo₁₂O₄₀)] (<b>2</b>), [Ag₄(bmtr)₂(H₂O)₂(SiMo₁₂O₄₀)] (<b>3</b>), and [Ag₄(bmtb)₃(SiMo₁₂O₄₀)] (<b>4</b>) (mmt = 1-methyl-5-mercapto-1,2,3,4-tetrazole, bmte = 1,2-bis­(1-methyl-5-mercapto-1,2,3,4-tetrazole)­ethane, bmtr = 1,3-bis­(1-methyl-5-mercapto-1,2,3,4-tetrazole)­propane, bmtb = 1,4-bis­(1-methyl-5-mercapto-1,2,3,4-tetrazole)­butane), have been synthesized under hydrothermal conditions. Single crystal X-ray diffraction analyses reveal that insertion of -(CH₂)_<i>n</i>- spacers into the reactant mmt ligand plays important roles in constructing multinuclear Ag^I clusters in the title compounds and tuning the formation of different multinuclear Ag^I clusters. In compound <b>1</b>, the mmt ligands link Ag^I ions forming a three-dimensional non-multinuclear self-penetrating framework with large dimension channels occupied by SiMo₁₂ polyanions. In <b>2</b>, a tetranuclear [Ag₄(bmte)₂(H₂O)₂]⁴⁺ and SiMo₁₂ anions arrange alternately forming a one-dimensional (1D) chain. The structure of compound <b>3</b> is similar to that of <b>2</b>, except for different coordination modes of Ag^I ions in tetranuclear clusters and SiMo₁₂ polyanions owing to the longer -(CH₂)₃- alkyl skeleton of bmtr ligand. Compound <b>4</b> exhibits a two-dimensional grid layer formed by a 1D Ag^I “ribbon” based on binuclear Ag^I clusters and bridging bmtb ligands with the longest -(CH₂)₄- alkyl skeleton. The SiMo₁₂ polyanions as tetradentate inorganic linkages reside in the grids. The influences of -(CH₂)_<i>n</i>- spacers on forming and tuning different multinuclear Ag^I clusters have been discussed. Furthermore, the photochemical catalysis and electrochemical properties of the title compounds have been studied